Composition for production of flame-retardant flexible polyurethane foams

ABSTRACT

The present invention provides a composition for flame-retardant flexible polyurethane foam comprising: (i) a polyol component; (ii) a polyisocyanate component; (iii) a halogen-free phosphate ester that meets the following conditions (a) to (d), and that contains at least one alcoholic hydroxyl group: (a) an acid value of 2 KOHmg/g or less, (b) a viscosity of 5 Pa·s or less at 25° C., (c) a hydroxyl value of 5 to 250 KOHmg/g, and (d) a weight average molecular weight of 200 to 2000; (iv) a tertiary amine carboxylate; (v) a silicone foam stabilizer; and (vi) a blowing agent. The composition for flame-retardant flexible polyurethane foam of the present invention can give a flexible polyurethane foam that has satisfactory flame retardant properties, as well as excellent properties such as better heat resistance, fogging resistance and scorch resistance and extremely low compression strain.

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application PCT/JP02/08361, filed on Aug. 20, 2002, whichclaims priority of Japanese Patent Application Nos. 2001-264165, filedon Aug. 31, 2001. The International Application was published under PCTArticle 21(2) in a language other than English.

TECHNICAL FIELD

The present invention relates to a composition for flame-retardantflexible polyurethane foam.

BACKGROUND ART

Polyurethane resins, which are typical of thermosetting resins, arerelatively inexpensive and are easy to mold, and the foamed productsthereof are widely used over the entire range of articles of daily use,including automotive parts. However, polyurethane resins are flammable,and once they ignite, they have a major drawback of carrying outuncontrollable combustion. Various efforts have thus been made toproduce flame-retardant polyurethane foam. Nowadays, flame retardance islegally compulsory in some fields featuring the use of polyurethane,such as automotive interiors.

Generally, in order to impart flame retardancy to polyurethane, themethod of adding a halogen-containing phosphate ester as a flameretardant is adopted. Additive-type flame retardants ofhalogen-containing monomeric phosphate ester are usually used, such astris(chloroethyl) phosphate and tris(chloropropyl) phosphate. However,these flame retardants tend to be vaporized at high temperature due totheir low molecular weight. When the polyurethane foam containing such aflame retardant is used for automotive sheet and the like, as thetemperature inside the automobile increases in summer or under similarhigh-temperature conditions, a phenomenon of fogging tends to occur inwhich phosphate components, amine catalysts contained in the startingmaterials, or salts of amine with hydrogen halides produced by thedecomposition of the phosphate components are vaporized or scatteredinside the automobile and the glass of the automobile becomes cloudy.Further, the flame retardant property of the foamed product is sometimesimpaired. The vaporized or scattered materials also pose the risk ofadversely affecting humans.

A method that has thus been proposed in order to reduce the amount offlame retardants which are vaporized is to use additive-type flameretardants of halogen-containing condensed phosphate oligomer. However,monomer components generally remain in an amount of about 5 to 20 wt %in oligomer types of flame retardants, so even when oligomer types offlame retardants are used, the problem of the flame retardant becomingvaporized at elevated temperatures cannot still be overcome due to thepresence of such low molecular weight components.

Other known flame retardants are additive-type flame retardants ofhalogen-containing highly condensed phosphate esters in which thephosphate esters are condensed to a higher degree in order to minimizethe amount of residual monomer components. However, such highlycondensed phosphate esters have poor workability because of their highviscosity, and tend to decompose, resulting in the formation of hydrogenhalide salts of amines, with the risk of scattering and adverse effectson other physical properties such as scorch resistance.

Furthermore, the aforementioned types of flame retardants all containhalogens, and there is concern that their vaporization might affecthumans and they produce dioxins when burned.

Although the use of additive-type flame retardants of halogen-freephosphate ester could overcome problems such as the formation ofhydrogen halide salts of amines and the production of dioxins whenburned, the vaporization of the phosphate esters itself cannot beprevented.

Methods that have thus been studied include preventing flame retardantsfrom being vaporized by using flame retardants with reactive functionalgroups, referred to as reactive flame retardants, which are incorporatedinto the resin skeleton of the polyurethane foam by reacting withstarting materials.

The polyurethane foam is formed by the reaction between isocyanategroups of a polyisocyanate and two types of hydroxyl groups, i.e.hydroxyl groups in the polyol and hydroxyl groups in water serving asthe blowing agent. However, when reactive flame retardants of phosphateester containing reactive functional groups are used, it is necessary tocontrol the reaction between the isocyanate groups and three differenttypes of reactive functional groups, making it difficult to fullysatisfy the intended properties of foamed product in the conventionalmanner.

Japanese Unexamined Patent Publication No. 2001-11302, for example,describes a method in which a reactive type of phosphate estercontaining alcoholic hydroxyl groups is used to produce aflame-retardant flexible polyurethane foam. Japanese Unexamined PatentPublication No. 2001-151919 describes a method in which both a reactivetype of phosphate ester containing alcoholic hydroxyl groups and anadditive type of oligomeric phosphate ester are used to produce aflame-retardant flexible polyurethane foam with good flame laminateproperty. In these methods, however, it is difficult to achieve thewell-balanced reaction between the three types of hydroxyl groups andthe isocyanate groups. Thus, open cells cannot be formed by simplyvarying the amount of the reactive phosphate ester and a closed cellfoam tends to be formed, resulting in the low air permeability and thehigh compressive strain of the foamed product.

DISCLOSURE OF THE INVENTION

A primary object of the present invention is to provide a compositionfor polyurethane foam capable of overcoming the drawbacks describedabove, that is, a composition for polyurethane foam containing areactive-type flame retardant of halogen-free phosphate ester, whichcomposition is capable of forming a flame-retardant flexiblepolyurethane foam with outstanding characteristics such as better flameretardant properties, excellent resistance to scorch and fogging, andlower compressive strain.

As a result of extensive research to overcome the drawbacks describedabove, the inventors accomplished the present invention upon findingthat a flame-retardant flexible polyurethane foam with excellent flameretardant properties, resistance to scorch and fogging, and lowercompressive strain can be obtained by using a specific halogen-freephosphate ester containing reactive functional groups as a flameretardant in combination with a salt of a tertiary amine compound with acarboxylic acid.

Specifically, the present invention provides the following compositionsfor polyurethane foam.

1. A composition for flame-retardant flexible polyurethane foamcomprising:

(i) a polyol component;

(ii) a polyisocyanate component;

(iii) a halogen-free phosphate ester that meets the following conditions(a) to (d), and that contains at least one alcoholic hydroxyl group;

-   -   (a) an acid value of 2 KOHmg/g or less,    -   (b) a viscosity of 5 Pa·s or less at 25° C.,    -   (c) a hydroxyl value of 5 to 250 KOHmg/g, and    -   (d) a weight average molecular weight of 200 to 2000;

(iv) a tertiary amine carboxylate;

(v) a silicone foam-stabilizer; and

(vi) a blowing agent.

2. A composition for flame-retardant flexible polyurethane foamaccording to the above item 1, which comprising 1 to 20 parts by weightof the phosphate ester specified in item (iii), 0.01 to 0.3 part byweight of the tertiary amine carboxylate, 0.5 to 2 parts by weight ofthe silicone foam stabilizer and 0.1 to 40 parts by weight of theblowing agent, per 100 parts by weight of the polyol component.

3. A composition for flame-retardant flexible polyurethane foamaccording to the above item 1 or 2, wherein the tertiary aminecarboxylate is a salt of aliphatic tertiary amine with carboxylic acid.

4. A composition for flame-retardant flexible polyurethane foamaccording to any one of the above items 1 to 3, wherein the phosphateester specified in item (iii) is a compound represented by the followingformula (I):

wherein R¹ is a C₁ to C₄ alkyl group, R² is a C₁ to C₃ alkylene group,R³ is a C₁ to C₃ alkyl group, and n is an integer of 1 to 10.

The composition for flame-retardant polyurethane foam of the presentinvention comprises the following components (i) to (vi) as essentialcomponents:

(i) a polyol component;

(ii) a polyisocyanate component;

(iii) a halogen-free phosphate ester that meets the following conditions(a) to (d), and that contains at least one alcoholic hydroxyl group;

-   -   (a) an acid value of 2 KOHmg/g or less,    -   (b) a viscosity of 5 Pa·s or less at 25° C.,    -   (c) a hydroxyl value of 5 to 250 KOHmg/g, and    -   (d) a weight average-molecular weight of 200 to 2000;

(iv) a tertiary amine carboxylate;

(v) a silicone foam stabilizer; and

(vi) a blowing agent.

The individual components contained in the composition for polyurethanefoam of the present invention are described below.

(i) Polyol Component

Examples of polyol components which can be used include polyolcomponents commonly used in the production of flexible polyurethanefoam, such as polyether polyols, polyester polyols and polymer polyols.

Examples of polyether polyols among these include polyether polyols witha hydroxyl value of about 25 to 70 KOHmg/g, which are obtained by therandom or block addition of alkylene oxides such as ethylene oxide andpropylene oxide to polyfunctional polyols, amine compounds or the like.Examples of polyfunctional polyols include glycols such as ethyleneglycol and propylene glycol; triols such as glycerol andtrimethylolpropane; polyols such as pentaerythritol, sorbitol andsucrose. Examples of amine compounds include ammonia, triethanolamine,ethylene diamine, diethylene triamine, aminoethyl piperazine andaniline.

Polyester polyols are compounds having terminal hydroxyl groups obtainedby the polycondensation of polyfunctional carboxylic acids andpolyfunctional hydroxyl compounds, preferably with a number averagemolecular weight of about 500 to 10,000, and more preferably about 1000to 5000. Examples of polyfunctional carboxylic acids include adipicacid, phthalic acid, succinic acid, azelaic acid and sebacic acid.Examples of polyfunctional hydroxy compounds include glycols such asethylene glycol, propylene glycol, butanediol and diethylene glycol, andpolyhydric alcohols such as glycerol, trimethylol propane andpentaerythritol.

Polymer polyols can be obtained by mixing a polyether polyol and anethylenically unsaturated monomer, and, when necessary, adding chaintransfer agents, dispersion stabilizers and the like to bring about theradical polymerization of the ethylenically unsaturated monomer in thepresence of a radical initiator. Examples of ethylenically unsaturatedmonomers include monomers containing cyano group such as acrylonitrileand methacrylonitrile; (meth)acrylic esters such as methyl(meth)acrylate, butyl (meth)acrylate, stearyl (meth)acrylate,hydroxyethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate anddimethylaminopropyl (meth)acrylate; monomers containing carboxyl groupsuch as acrylic acid, methacrylic acid, itaconic acid, maleic acid andfumaric acid; acid anhydride monomers such as maleic anhydride anditaconic anhydride; hydrocarbon compounds such as butadiene, isopreneand 1,4-pentadiene; aromatic hydrocarbon compounds such as styrene,α-methyl styrene, phenylstyrene and chlorostyrene; halogene-containingmonomers such as vinyl chloride and vinylidene chloride; vinyl etherssuch as vinyl ethyl ether and vinyl butyl ether; vinyl ketones such asvinyl ethyl ketone; vinyl esters such as vinyl acetate; acrylamides suchas acrylamide, N,N-dimethylacrylamide, N-isopropylamide,N,N-dimethylaminopropyl acrylamide and methylene bisacrylamide; andmethacrylamides such as N,N-dimethyl methacrylamide. Such ethylenicallyunsaturated monomers may be used alone or in combinations of two ormore.

The aforementioned polyol components can be used alone or incombinations of two or more, depending on the properties required of thepolyurethane foam that is to be prepared.

For example, a foamed product with high elasticity can be obtained whenthe aforementioned polyether polyol and polymer polyol are used in aproportion, based on the combined weight of the two, of 30 to 90 wt % ofthe former and 70 to 10 wt % of the latter, and preferably 40 to 80 wt %of the former and 60 to 20 wt % of the latter.

(ii) Polyisocyanate Component

Examples of polyisocyanate components which can be used include variouspolyisocyanate compounds having two or more isocyanate groups, which areheretofore used in polyurethane resin compositions. Examples of suchpolyisocyanate compounds include aromatic polyisocyanates, aliphaticpolyisocyanates and alicyclic polyisocyanates, as well as mixtures oftwo or more of such polyisocyanates, and modified polyisocyanatesobtained by the modification of such polyisocyanates. Specific examplesof such polyisocyanate compounds include polyisocyanates such astolylene diisocyanate, diphenylmethane diisocyanate, polymethylenepolyphenylene polyisocyanate (crude MDI), xylylene diisocyanate,isophorone diisocyanate and hexamethylene diisocyanate; and modifiedproducts of such polyisocyanates, such as carbodiimide modifiedproducts, burette modified products, dimmers and trimers. Prepolymerswith terminal isocyanate groups obtained from such polyisocyanates andactive hydrogen-containing compounds can also be used.

It is especially preferred in the present invention to use, alone or incombination, tolylene diisocyanates, including isomers such as2,4-tolylene diisocyanate, 2,6-tolylen diisocyanate and the like.

The amount in which the polyisocyanate component is used is notparticularly limited, but is usually an amount resulting in anisocyanate index of about 90 to 120, preferably about 95 to 115, andeven more preferably about 100 to 110.

(iii) Flame Retardant

The flame retardant is a halogen-free phosphate ester which meets thefollowing conditions (a) to (d) and which contains at least onealcoholic hydroxyl group (sometimes referred to below as “reactivephosphate ester”):

-   -   (a) an acid value of 2 KOHmg/g or less,    -   (b) a viscosity of 5 Pa·s or less at 25° C.,    -   (c) a hydroxyl value of 5 to 250 KOHmg/g, and    -   (d) a weight average molecular weight of 200 to 2000.

The alcoholic hydroxyl group allows such phosphate esters to react withthe polyisocyanate compound in the starting materials so as to beincorporated into the resin skeleton of the polyurethane foam, thuspreventing them from being vaporized. The lack of halogen can preventharmful effects on humans caused by the vaporization, the production ofdioxins when burned, and the like.

The acid value of the phosphate ester is 2 KOHmg/g or less. A higherlevel of the acid value will result in the loss of catalytic activityduring foaming, making it difficult to obtain foamed products. Althoughit would appear that the amount of catalyst could be increased toenhance the catalytic activity, this is economically disadvantageous andcan also lead to foamed products with lower physical properties, and istherefore not preferred.

The phosphate ester has a viscosity of 5 Pa·s or less at 25° C. andpreferably has a viscosity of 4 Pa·s or less at 25° C. A viscosityhigher than that will impose a greater stirring load during theproduction of the foamed product, and will not allow the phosphate esterto be uniformly dispersed, which might adversely affect the propertiesof the resulting formed product.

The hydroxyl value of the phosphate ester is 250 KOHmg/g or less. Ahigher value will make it difficult to control the reaction, and willtend to result in the formation of closed cells, thus adverselyaffecting the properties such as the air permeability and compressivestrain of the foamed product.

The weight average molecular weight of the phosphate ester is within therange of 200 to 2000. A molecular weight lower than this range willresult in the vaporization of the phosphate ester by the heat ofreaction before reaction with the isocyanate groups, resulting in lowerflame retardant properties, and the foamed product will have coarselyformed cells. A molecular weight higher than the above range will resultin a higher viscosity, and will thus impose a greater stirring loadduring the production of the foamed product, resulting in poor phosphateester dispersion and foamed product with inferior properties.

Any phosphate ester meeting the above conditions can be used as theflame retardant in the present invention. Specific examples of suchflame retardants include those represented by formula (I) to (IV) below.

(wherein R¹ is a C₁ to C₄ alkyl group, R² is a C₁ to C₃ alkylene group,R³ is a C₁ to C₃ alkyl group, and n is an integer of 1 to 10).

(wherein R¹ is a C₂ to C₄ alkylene group, R² is a C₁ to C₄ alkyl group,R³ is a C₁ to C₄ alkylene group, 1 is an integer of 1 to 10, m is aninteger of 1 to 10 and n is an integer of 1 to 10).

(wherein R¹ is a C₁ to C₄ alkyl group, R² is a C₁ to C₄ alkylene group,R³ is a C₂ to C₄ alkylene group, m is an integer of 1 to 10, and n is aninteger of 1 to 10).

(wherein R¹ is a C₁ to C₄ alkyl group, R² is a C₂ to C₄ alkylene group,m is an integer of 1 to 10 and n is an integer of 1 to 10).

In the aforementioned general formulas, C₁ to C₄ alkyl groups are linearor branched alkyl groups with 1 to 4 carbon atoms, specific examples ofwhich include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl and tert-butyl. Examples of C₁ to C₄ alkylenes include linearmethylenes such as methylene, ethylene, trimethylene and tetramethylene,and branched methylenes such as isopropylene and isobutylene.

The amounts of the aforementioned reactive phosphate esters to be usedis determined according to the level of flame retardancy that isdesired. An insufficient amount does not impart a satisfactory flameretardant effect. In contrast, an excessive amount may adversely affectthe physical properties of the resulting foam. Generally, the amount ofthe reactive phosphate esters is preferably about 1 to about 20 parts byweight per 100 parts by weight of polyol component.

(iv) Tertiary Amine Carboxylate

It is necessary to use a tertiary amine carboxylate in the compositionfor polyurethane foam of the present invention. A salt of aliphatictertiary amine with carboxylic acid is particularly preferred as thetertiary amine carboxylate.

Amine compounds are generally known to have catalytic activity inreactions between hydroxyl groups and isocyanate groups inpolyisocyanate compounds. In the composition for polyurethane foamcontaining a reactive phosphate ester, components with hydroxyl groupsinclude the reactive phosphate ester and the blowing agent in additionto the polyol, and thus the composition contains at least three types ofcomponents with hydroxyl groups. The use of ordinary amine catalyst ormetal catalyst alone in such a composition does not result in the properbalance of reaction between the isocyanate groups and the three types ofhydroxyl groups, and tends to produce compressive strain in theresulting foamed product.

In contrast, when a tertiary amine carboxylate is used as a catalyst,the reactions between the isocyanate groups and the three types ofhydroxyl groups progress with a good balance, giving a foamed productwith excellent physical properties.

Specific examples of tertiary amines for forming tertiary aminecarboxylates-include aliphatic tertiary amines such asbis(2-dimethylaminoethyl) ether, N-methyl-N′-(2-dimethylaminoethyl)piperazine, N,N,N′N′-tetramethyl-1,6-hexamethylenediamine,N,N,N′N′,N″-pentamethyl diethylenetriamine, N,N,N′N′-tetramethylethylenediamine, and 1,4-diazabicyclo-[2,2,2]-octane. Examples ofcarboxylic acids for forming salts with such tertiary amines includealiphatic monocarboxylic acids with about 1 to 8 carbon atoms, such asformic acid and acetic acid.

The amino groups of the tertiary amines in the tertiary aminecarboxylates which can be used in the present invention are partially orcompletely neutralized by the carboxylic acid. The tertiary aminecarboxylates can be used alone or in combinations of two or more.

The tertiary amine carboxylate is preferably used in an amount of about0.01 to 0.3 part by weight per 100 parts by weight of polyol component.When the metal catalyst and ordinary amine catalyst described below arenot used, the tertiary amine carboxylate is preferably used in an amountof about 0.02 to 0.3 part by weight per 100 parts by weight of polyolcomponent to ensure sufficient catalytic action in producing the resin.

(v) Silicone Foam Stabilizer

Block copolymers of dimethylsiloxane and a polyether are usually used assilicone foam stabilizers, and can have various forms, such as linear,branched, or pendant form, but especially, branched or pendantcopolymers are used in many cases. The silicone foam stabilizer used inthe present invention is not particularly limited. Any silicone foamstabilizer heretofore used for flexible polyurethane foam may be used.

The use of silicone foam stabilizer provides effects such as preventingthe coalescence of bubbles and stabilizing the cell films in addition tofacilitating the mixing and emulsification of the starting materials andthe dispersion of gases involved, thereby enabling foams with goodproperties to be obtained.

Although the amount of the silicone foam stabilizer to be used is notparticularly limited, it is preferably about 0.5 to 2 parts by weightper 100 parts by weight of polyol component.

(vi) Blowing Agent

As the blowing agent in the composition for a polyurethane foam of thepresent invention, known blowing agents heretofore used in thecompositions for flexible polyurethane foam are suitably selectedaccording to the properties required of the foamed product.

Water is a typical example of such a blowing agent, and other examplesinclude methylene chloride, n-butane, isobutane, n-pentane, isopentane,dimethyl ether, acetone, CO₂, etc. Depending on desired density andother properties of the foamed product, such blowing agents can be usedalone or in combinations of two or more in the manner known in the art.

The amount of the blowing agent to be used is not particularly limited,but the amount ordinarily ranges from about 0.1 to 40 parts by weightper 100 parts by weight of polyol component.

Other Components

(a) Catalyst

The tertiary amine carboxylate used in the composition of the presentinvention has catalytic activity in the reaction between the hydroxylgroups and the isocyanate groups, but has relatively low catalyticactivity in the reaction between the polyisocyanate component and polyolcomponent, that is, the resinification reaction. Known catalystcomponents can therefore also be used, when necessary, to promote theresinification reaction in cases of low reactivity between the polyolcomponent and polyisocyanate component. Such catalysts include ordinaryamine catalysts and metal catalysts.

Examples of ordinary amine catalysts include tertiary amine compoundswhich do not form salts with carboxylic acids, and can usually be usedin an amount of about 0.01 to 0.1 part by weight per 100 parts by weightof polyol component. Such ordinary amine catalysts are preferably usedin an amount such that the total amount with the aforementioned tertiaryamine carboxylates is within the range of about 0.02 to 0.3 part byweight per 100 parts by weight of polyol component.

Metal catalysts are typically organometallic compounds containing metalcomponent such as tin, copper, lead, zinc, cobalt or nickel. Tincatalysts such as dibutyl tin dilaurate and stannous octoate showparticularly good catalytic activity.

Metal catalyst is preferably used in an amount ranging between about0.01 and 1 part by weight per 100 parts by weight of polyol component.

The use of the metal catalyst within the aforementioned range, togetherwith a amine catalyst such as the tertiary amine carboxylate or amixture of the tertiary amine carboxylate and the ordinary aminecatalyst, can allow the resinification and foaming reaction to progresswith a good balance.

(b) Flame Retardant

Phosphate esters with no reactive functional group (additive type ofphosphate ester) may also be added, if needed, as flame retardants tothe composition for polyurethane foam of the present invention, providedthat the foamed product is not thereby adversely affected.

Examples of such additive types of phosphate esters include oligomertypes of phosphate esters, such as resorcinol bis(diphenylphosphate),bisphenol A bis(diphenylphosphate), resorcinolbis(bis(2,6-dimethylphenyl)phosphate), hydroquinonebis(bis(2,6-dimethylphenyl)phosphate) and biphenolbis(bis(2,6-dimethylphenyl)phosphate); and monomer types of phosphateesters, such as triphenyl phosphate, naphthyl diphenyl phosphate,dinaphthylphenyl phosphate, tricresyl phosphate, tributoxyethylphosphate and diphenyl-2-ethylhexyl phosphate.

Additive types of phosphate esters are preferably used in an amount ofabout 40 parts by weight or less, and more preferably about 0.1 to 30parts by weight, per 100 parts by weight of polyol component.

The aforementioned additive types of phosphate esters are preferablyhalogen-free oligomer types of phosphate esters for the sake ofpreventing fogging and adverse effects on humans.

It is effective to use low-viscosity additive types of phosphate esterstogether with reactive phosphate esters in order to lower the viscosityof the polyurethane composition as a whole and improve the workability,so as to give foamed product with better physical properties.

(c) Other Components

Additives such as colorants, crosslinkers, antioxidants, UV absorbents,agents for preventing hydrolysis, fillers and the like can also beadded, if needed, to the composition for polyurethane foam of thepresent invention. The type and amount of such additives are notparticularly limited. Commonly used additives can be used in thenormally used range.

Method for Producing Foamed Product

Polyurethane foam can be produced from the composition for polyurethanefoam of the present invention according to methods usually employed inthe art. The polyurethane foam can be obtained, for example, by one-shotmethods in which the polyol component, water, catalyst, flame retardant,foam stabilizer and the like are simultaneously mixed with thepolyisocyanate component to bring about foaming through their reaction;prepolymer methods in which a portion of the polyol component is reactedwith all of the polyisocyanate component, and the other components aremixed with the resulting prepolymer to bring about a reaction; and othermethods. In these methods, the catalyst is usually pre-mixed with thepolyol component for use in the form of a homogenous solution ordispersion.

The composition for flame-retardant flexible polyurethane foam of thepresent invention results in flexible polyurethane foam that hassatisfactory flame retardant properties, as well as outstandingcharacteristics such as good heat resistance, excellent resistance tofogging and scorch, and extremely low compressive strain. Suchflame-retardant flexible polyurethane foam can be effectively used, forexample, in automobile seats or furniture such as sofas and beds.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention is illustrated in further detail with reference to thefollowing examples.

EXAMPLES 1 to 5 AND COMPARATIVE EXAMPLES 1 to 4

Flexible polyurethane foams were produced by the following one-shotmethod using the compositions having the formulations shown in Tables 1and 2.

First, all components except for the polyisocyanate component wereblended in the predetermined proportions, and were uniformly kneaded bybeing stirred at 3000 rpm for 1 minute in a stirring device. Thepolyisocyanate component was added, the mixture was stirred for another5 to 7 seconds at 3000 rpm, and the mixture was quickly poured intocardboard boxes with a square cross section.

Foaming took place immediately and maximum volume was reached after afew minutes. The mixture was cured for another 15 minutes in an oven at80° C. The resulting foamed product was a flexible white polyurethanefoam with open cells.

The symbols in Tables 1 and 2 indicate the following components.

1. Polyol Component

(1) MN-3050

Trifunctional propylene-based polyether polyol (number average molecularweight: 3000; hydroxyl value: 56.0 KOHmg/g) (tradename: MN-3050 ONE, byMitsui Takeda Chemicals Inc.)

2. Reactive Phosphate Ester Flame Retardant

(1) TF-J12

Phosphate ester represented by following formula and having thefollowing properties (by Daihachi Chemical Industry Co., Ltd.)

-   -   hydroxyl value: 225 KOHmg/g    -   acid value: 0.08 KOHmg/g    -   viscosity (25° C.): 4.0 Pa·s    -   weight average molecular weight: 243        (2) Exolit OP-550

Phosphate ester with hydroxyalkyl groups having the following properties(tradename: Exolit OP-550, by Clariant Corporation)

-   -   phosphorus content: 17.0%    -   hydroxyl value: 130 KOHmg/g    -   acid value: 1.3 KOHmg/g    -   viscosity (25° C.): 2.1 Pa·s    -   weight average molecular weight: 863        (3) Fyrol-PNX

Phosphate ester with hydroxyalkyl groups having the following properties(tradename: Fyrol-PNX, by Akuzo Nobel Chemicals Co., Ltd.)

-   -   phosphorus content: 19.0%    -   hydroxyl value: 20 KOHmg/g    -   acid value: 1.5 KOHmg/g    -   viscosity (25° C.): 2.0 Pa·s    -   weight average molecular weight: 945        3. Additive-Type Phosphate Ester Flame Retardant (Halogen-Free        Phosphate Esters)        3.1 Oligomer Type        (1) CR-733S

Resorcinol bis (diphenylphosphate) (tradename: CR-733S, by DaihachiChemical Industry Co., Ltd.)

3.2 Monomer Type

(1) TBXP

Tributoxyethyl phosphate (tradename: TBXP, by Daihachi Chemical IndustryCo., Ltd.)

4. Polyisocyanate Component

(1) T-80

-   -   Tolylene diisocyanate (2,4-/2,6-isomer ratio=80/20)    -   (tradename: Cosmonate T-80, by Mitsui Takeda Chemicals Inc.)        5. Catalyst        5.1 Tertiary Amine Carboxylate        (1) TOYOCAT-ETF

Salt of Bis(2-dimethylaminoethyl) ether with acetic acid (tradename:TOYOCAT-ETF, by Tosoh Corporation)

5.2 Ordinary Amine Catalyst

(1) TOYOCAT-ET

Bis(2-dimethylaminoethyl) ether (tradename: TOYOCAT-ET, by TosohCorporation)

(2) TEDA-L33

1,4-diazabicyclo-[2,2,2]-octane (33% dipropylene glycol solution(tradename: TEDA-L33, by Tosoh corporation)

5.3 Tin Catalyst

(1) DABCO T

Stannous octoate (tradename: DABCO T, by Sankyo Air Products Co., Ltd.)

6. Silicone Foam Stabilizer

(1) L-580

(tradename: L-580, by Nippon Unicar Co., Ltd.)

(2) L-688

(tradename: L-688, by Witco Corporation)

(3) SZ-1136

(tradename: SZ-1136, by Nippon Unicar Co., Ltd.)

Samples were cut out from the polyurethane foams obtained in the mannerdescribed above, and the properties were measured by the following testmethods. The results are given along with the components and theirproportions in Tables 1 and 2.

(1) Flammability Test

Test method: based on FMVSS-302

Foam piece: length 250 mm, width 70 mm

Foam thickness: 13 mm

Evaluated by the following basis:

-   -   NB: no burning; SE: self-extinguishing;    -   BN: burning        (2) Compression Strain

Test method: based on JIS K-6382

Foam piece: length 6 cm, width 6 cm, thickness 5 cm

The surface of 6 cm×6 cm foam pieces was compressed to 50% thickness for22 hours at 70° C., the pressure was released, the foam thickness wasthen measured, and the percentage of the reduction in thickness relativeto the thickness before compression was evaluated as the compressionstrain. For example, if the thickness returned to 4 cm, the compressionstrain is (1-4/5)×100=20%.

(3) Scorch Test

Samples were treated for 3 minutes in a microwave oven (500 W) and thenheated for 2 hours at 140° C. The change in the color (scorching) of thetest pieces at that time was determined on the basis of the followingscale by measuring the yellow index (YI) with a calorimeter.

A: YI 30 or less (no change in color)

B: YI 31 to 50 (slight change in color)

C: YI 51 to 70 (color changed)

D: YI 71 or more (considerable change in color)

TABLE 1 Examples 1 2 3 4 5 Amounts Polyol MN-3050 100 100 100 100 100(weight Component parts) Tertiary amine TOYOCAT-ETF 0.3 0.2 0.2 0.2 0.2carboxlate catalyst Ordinary amine TOYOCAT-EF 0.1 catalyst TEDA-L33 0.10.1 0.1 Tin catalyst DABCO T 0.25 0.25 0.25 0.25 0.25 Water 2.5 4.5 4.54.5 4.5 Methylene chloride 3 5 3 3 Reactive TF-J12 2 5 15 phosphateester Exolit OP-550 10 flame retardant Fyrol-PNX 10 Additive-typeCR-733S 15 phosphate ester TBXP 5 flame retardant Silicone foam SZ-11361 1 stabilizer L-688 1 L-580 1 1 Polyisocyanate T-80 38.5 54.1 56.2 55.153.3 Component Properties Flammability test SE NB NB NB SE Compressionstrain (%) 4.2 5.3 7.4 8.2 9.3 Scorching property A A A B B

TABLE 2 Comparative example 1 2 3 4 Amounts Polyol MN-3050 100 100 100100 (weight Component parts) Tertiary amine TOYOCAT-ETF carboxylatecatalyst Ordinary amine TOYOCAT-EF catalyst TEDA-L33 0.3 0.3 0.2 0.2 Tincatalyst DABCO T 0.25 0.25 0.25 0.25 Water 4.5 2.5 4.5 4.5 Methylenechloride 3 3 3 Reactive TF-J12 7.5 2 phosphate ester Exolit OP-550 10flame retardant Fyrol-PNX 10 Additive-type CR-733S phosphate ester TBXP2.5 flame retardant Silicone foam SZ-1136 stabilizer L-688 L-580 1 1 1 1Polyisocyanate T-80 55.1 38.5 55.1 55.1 Component PropertiesFlammability test NB SE NB NB Compression strain (%) 33.0 12.0 43.0 45.0Scorching property B A C C

The above results clearly show that the composition for flame-retardantflexible polyurethane foam of the present invention, which contained areactive phosphate ester flame retardant and a tertiary aminecarboxylate, resulted in foamed products with excellent properties, i.e.good flame retardant properties, no scorching and extremely lowcompression strain.

In contrast, the compositions of Comparative Examples 1 to 4, whichcontained no tertiary amine carboxylates but only reactive phosphateester flame retardants, resulted in foamed product with low commercialvalue due to high compression strain and occasional scorching.

1. A composition for flame-retardant flexible polyurethane foamcomprising: (i) a polyol component; (ii) a polyisocyanate component;(iii) a halogen-free phosphate ester that meets the following conditions(a) to (d), and that contains at least one alcoholic hydroxyl group; (a)an acid value of 2 KOHmg/g or less, (b) a viscosity of 5 Pa·s or less at25° C., (c) a hydroxyl value of 5 to 250 KOHmg/g, and (d) a weightaverage molecular weight of 200 to 2000; (iv) a tertiary aminecarboxylate; (v) a silicone foam stabilizer; and (vi) a blowing agent.2. The composition according to claim 1, which comprises 1 to 20 partsby weight of the phosphate ester specified in item (iii), 0.01 to 0.3part by weight of the tertiary amine carboxylate, 0.5 to 2 parts byweight of the silicone foam stabilizer and 0.1 to 40 parts by weight ofthe blowing agent, per 100 parts by weight of the polyol component. 3.The composition according to claim 1, wherein the tertiary aminecarboxylate is a salt of aliphatic tertiary amine with carboxylic acid.4. The composition according to claim 1, wherein the phosphate esterspecified in item (iii) is a compound represented by the followingformula (I):

wherein R¹ is a C₁ to C₄ alkyl group, R² is a C₁ to C₃ alkyl group R³ isa C₁ to C₃ alkyl group and n is an integer of 1 to
 10. 5. Thecomposition according to claim 2, wherein the tertiary amine carboxylateis a salt of aliphatic tertiary amine with carboxylic acid.
 6. Thecomposition according to claim 2, wherein the phosphate ester specifiedin item (iii) is a compound represented by the following formula (I):

wherein R¹ is a C₁ to C₄ alkyl group, R² is a C₁ to C₃ alkylene group,R³ is a C₁ to C₃ alkyl group and n is an integer of 1 to
 10. 7. Thecomposition according to claim 3, wherein the phosphate ester specifiedin item (iii) is a compound represented by the following formula (I):

wherein R¹ is a C₁ to C₄ alkyl group, R² is a C₁ to C₃ alkylene group,R³ is a C₁ to C₃ alkyl group and n is an integer of1 to 10.